Generally, a curtain wall or a double layered window composed of indoor and outdoor windows is installed to an apartment building or a mixed-use residential building.
In particular, a double layered window has advantages of ensuring insulation and sound absorption. However, as construction of a balcony expansion is legalized, general consumers prefer double layered windows or double curtain walls in which a gap between indoor and outdoor windows is decreased, in order to ensure a wide indoor area.
FIG. 1 is a schematic view showing a structure of a general double layered window. A conventional double layered window includes a window frame 10 fixed to a wall (not shown), sash frames 20 and 30 installed to the window frame 10, and an indoor window 40 and an outdoor window 50 respectively installed to the sash frames 20 and 30, and a predetermined space 60 is defined between the indoor window 40 and the outdoor window 50.
A double layered window having the narrow space 60 between the indoor window 40 and the outdoor window 50 has advantages in that the excellent insulation performance and sound absorption can be maintained and a wide indoor area can also be ensured. However, in winter, a large amount of dew water 70 (see FIG. 1) is condensed on an inner side (a side toward an indoor area) of the outdoor window 50 due to a great difference between indoor temperature and outdoor temperature.
The dew water may be introduced into a room through a gap between the indoor window 40 and the sash frame 20, and the dew water introduced into the room causes various problems such as must, stain, dirt, and frost. Also, the dew water generated on the window disturbs a field of view from the indoor area to the outside.
Particularly, there is a disadvantage in that in order to solve this problem occurring in the space 60 between the indoor window 40 and the outdoor window 50, the indoor window 40 or the outdoor window 50 should be frequently open for ventilation in the double layered window.